Vertolot,
As Geoff has said
It is not therefore possible to use PC1 offshore - PC2 (enhanced) is as good as it's going to get - for the time being.
This needs to be explained:
Firstly Bpaggi is correct that, with the appropriate helicopter, PC1 can be available for a proportion of the time; for the AW139, that will be a larger proportion than for some other less powerful types. It is for that reason, PC1 cannot be mandated.
If your RFM contains a Category A Helideck (S76C+) or a PC2 Helideck (S92A and B412) procedure that is the one you should use. You should be aware of limitations of a Cat A Helideck procedure which could prevent its use (which could be the requirement for additional equipment or specific deck markings).
One of the Cat A limitations might be the size of the take-off surface; look at the RFM for your helicopter and check the minimum size, in most cases it will be more than the 1D provided as a Standard for helidecks offshore. This limitation is more to do with the ability to retain a visual reference within the FOV (this will be more severe on toadstool type well-head platforms – this might be mitigated with better procedures using oblique departures).
PC2e remains silent on the size of the helideck.
Another might be the crosswind limitations of the procedure; all of you who fly offshore will be familiar with the requirement for a 180° obstacle free segment (based upon the 5 in 1 falling gradient). If the wind is strong and outside that segment, a take-off using the Cat A procedure might not be possible within the limits of the procedure. In addition, a Category A procedure is deterministic and depends for obstacle clearance on a reasonably accurate assessment of the wind; if the wind is from the obstacle segment it is likely to be turbulent (and contain vertical components); establishing a pure wind vector will be problematic.
PC2e relies upon normal cross wind limitations and uses notional obstacle clearance (deck-edge clearance and drop-down appropriate to the height of the helideck); it is implicitly understood that take-off into the Limited Obstacle Segment (a 210° segment in which the 180° segment is contained) can be performed because it should only occur when cross wind limitations would be exceeded, at which time the helicopter will be approaching minimum drop-down regimes. Most offshore pilots will know that the most extreme of these manoeuvres is when the pilot (in a strong wind) is facing directly into the obstacle segment, when a sideways rotation is taken from the RP.
Lastly, the Cat A procedure assumes: a stable helideck; a continuous approach profile from the LDP; and a reject following a failure before TDP. Operations to a moving deck tend to fall outside those parameters (see the discussion in ACJ to Subpart H paragraph 7.4.2).
Now to answer Vertolot’s question:
The procedure needs to provide: a vertical acceleration segment (providing inertial energy); kinetic energy in the Rotor speed (permitting droop); and potential energy in the height of rotation (the RP). It must avoid a manoeuvre which results in a move backwards into obstacles or puts the pilot in a position where visual reference cannot be maintained following an engine failure before RP (which might also be a factor in a too aggressive vertical segment – for example when the helicopter is light). This limits the maximum height of the RP (or results in a torque delta).
The procedure and RP chosen by the manufacturer will provide an optimised combination of all of the above. These manoeuvres are complex and are associated with the calculation of take-off masses to achieve deck-edge clearance and minimising drop-down whilst staying within the limitation of the helicopter. The manufacturer could provide two graphs: the first will provide the maximum mass for which deck-edge clearance will be achieved; the second will modify that mass to reduce drop down. The pilot should use a modified mass that ensures compliance with the appropriate rules.
In providing the take-off mass, the graphs might also ensure that the second segment climb performance (150ft/min at Vy and 1000ft) and AEO HOGE are provided (B412). The pilot is still responsible for ensuring that en-route performance is achieved.
With respect to larger decks: manufacturers are also considering providing distance to descent below the helideck level (could also be seen as the absolute deck-edge clearance). This would ensure that a take-off can be taken from the TPM (bum line) on a deck which is larger than 1D without compromising the clearance.
Jim